Radiation dosimeters generally refer to devices that measure exposure to ionizing radiation and play vital role for workers in certain industries where there is routine radiation exposure. It is important for these workers to monitor the cumulative dose over time to ensure that their exposure does not exceed safe levels. There are a number of types of radiation dosimeters available that fall into two general classes. The first class is referred to as a “passive” dosimeter that is sensitive to ionizing radiation and records a value of cumulative radiation dose (sometimes referred to as an “effective dose” or “equivalent dose” value measured in “sieverts” (e.g. Sv)). Typical embodiments of passive dosimeter do not have the capability to actively communicate the dose value to the user. The second class of dosimeter is referred to as an “active” dosimeter, which provides a communication reporting of the dose value to the user. Also, many embodiments of active dosimeter typically include an alarm function that provides the user with an audible and/or visual indication that a threshold dose value has been reached.
Active dosimetry for ionizing radiation has traditionally focused on measurements of what is referred to as a “personal dose equivalent”. The term “personal dose equivalent” as used herein generally refers to a quantity of ionizing radiation representing a safety threshold for exposure recommended by the International Commission on Radiation Units and Measurements (ICRU) for the dose equivalent in tissue at depth (d) below a specified point on the body. Examples of personal dose equivalents include a deep dose equivalent safety threshold value of about Hp(10) (e.g. for thoracic exposure) and a surface dose equivalent safety threshold value of about Hp(0.07) (e.g. for skin exposure). Those of ordinary skill in the related art appreciate that it is advantageous to separately monitor dose equivalent values for extremities (fingers, hands, wrists) and eye doses that may include a safety threshold value of about Hp(3) for personnel who may be routinely exposed as part of their profession, such as for example personnel who work in the fields of interventional radiology and cardiology as well as the nuclear power industry.
Passive dosimetry devices, such as thermoluminescent dosimeters (TLD) or what are referred to as “integrating dosimeters”, have been used to monitor extremity exposure to radiation. Some embodiments of integrating dosimeter may be able to communicate a reading to the user, however such devices do not provide real-time notification to users when they are receiving potentially damaging radiation exposure. Rather, embodiments of integrating dosimeter devices provide a one-time cumulative reading of exposure that occurs over an extended period of time, where the exposure reading is typically provided when it is too late to take action during the period of actual exposure to the ionizing radiation. True active dosimetry provides a significant benefit over passive dosimetry because users can be informed in “real-time” when they have entered a radiation field that poses a short or long term danger, and providing the users with the opportunity to remove themselves from harm's way. The term “real-time” as used herein typically refers to reporting, depicting, or reacting to events at the same rate and sometimes at the same time as they unfold, rather than delaying a report or action.
Traditional active dosimeters have been too bulky to wear (e.g. over 2.5 cm wide, 40 cc in volume, and 50 gm) anywhere other than on a user's torso. For example, traditional bulky and heavy active dosimeters can be distracting to a user, increase user fatigue, and limit a user's freedom of movement. All of these aspects of traditional active dosimeters hinder the user's ability to effectively perform tasks required by their job.
Therefore, it is appreciated that it is highly desirable to have a light and compact active dosimetry device that is comfortably wearable on or near the extremities, including fingers, hands, wrists, legs, ankles, feet, brain, uterus (e.g. for measuring fetal exposure), and eyes.